1. Technical Field
The disclosure relates to a power factor correction convertor, and more particularly to a common-core power factor correction resonant converter.
2. Related Art
In general, the circuit structure of a power factor correction converter usually uses the inductors as energy storage devices. The inductor further combines with the boost topology control architecture to achieve power factor correction effect such that the energy may be transferred to the loads. The output voltage of this type of converter must be higher than the voltage of the line power source. Thus the circuit is not suitable for low-voltage output. Therefore, it is necessary to change the circuit to the step-down circuit type, such as the Forward Converter. However, this circuit can not provide high power factor function.
In general, the boost converter requires complex control circuits, such as analog multiplier and other circuit elements to generate a high power factor and regulate the output, in order to achieve high power factor correction. In addition, the aforementioned structure further requires circuits having functions of frequency jitter, a quasi resonant, or a valley switching in order to reduce the Electromagnetic Interference (EMI).
In addition, due to the introduction of the boost topology control architecture for the power factor correction, the output voltage is raised to a higher voltage level, such as 600V. Therefore, a relatively high Drain-Source withstand voltage element (for example, more than 600V power components) must be considered when choosing the switching elements in the framework.
In view of this, the existing technology provides a power factor correction resonant converter, as shown FIG. 1, in order to solve previous problems. The Power Factor Correction resonant converter 100 uses the component 110 for soft switching, so that the input line voltage charges the capacitance CP to produce a charge-storage capacitor voltage VCP. Then the energy transferring operation is conducted by the soft switching operation through element 120, such that the charge-storage capacitor voltage VCP is converted to an output power.
Furthermore, the charge-storage capacitor voltage VCP of the power factor correction resonant converter 100 is charged to the same voltage level as the input line voltage at most. Therefore, a relatively low withstand voltage element can be used. However, the power factor correction resonant converter adopts two separate inductors (elements 110 and 120, respectively), and is implemented by using five diodes, such that the cost and the volume of the circuit elements increase, and the component conduction loss also increase. Therefore, the power factor correction circuit still needs improvement.